Method for making semimetal compound of pt

ABSTRACT

The disclosure relates to a method for making semimetal compound of Pt. The semimetal compound is a single crystal material of PtSe 2 . The method comprises: placing pure Pt and pure Se in a reacting chamber as reacting materials; evacuating the reacting chamber to be vacuum less than 10 Pa; heating the reacting chamber to a first temperature of 600 degrees Celsius to 800 degrees Celsius and keeping for 24 hours to 100 hours; cooling the reacting chamber to a second temperature of 400 degrees Celsius to 500 degrees Celsius and keeping for 24 hours to 100 hours at a cooling rate of 1 degrees Celsius per hour to 10 degrees Celsius per hour to obtain a crystal material of PtSe 2 ; and separating the excessive reacting materials from the crystal material of PtSe 2 .

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. § 119 fromChina Patent Application No. 201610862880.2, filed on Sep. 28, 2016, inthe China Intellectual Property Office, the disclosure of which isincorporated herein by reference. This application is related toapplications entitled, “SEMIMETAL COMPOUND OF Pt AND METHOD FOR MAKINGTHE SAME”, filed **** (Atty. Docket No. US60556).

BACKGROUND 1. Technical Field

The present disclosure relates to a semimetal compound of Pt and methodfor making the same.

2. Description of Related Art

Three-dimensional semimetals are important hosts to exotic physicalphenomenon such as giant diamagnetism, linear quantum magnetoresistance,and quantum spin Hall effect. Three dimensional Dirac fermions can beviewed as three dimensional version of graphene and have been realizedin Dirac semimetals.

Cd₃As₂, Na₃Bi, K₃Bi, and Rb₃Bi are found as three-dimensional Diracsemimetals. However, all the Cd₃As₂, Na₃Bi, K₃Bi, and Rb₃Bi are type-IDirac semimetals having a vertical cone of electron energy band as shownin FIG. 1. The type-I Dirac semimetals shows spin degenerate conicaldispersions that cross at isolated momenutum points (Dirac points) inthree dimensional momentum space. In a topological Dirac semimetal, themassless Dirac fermions are stabilized by crystal symmetry and could bedriven into various topological phases. When breaking the inversion ortime-reversal symmetry, the doubly de-generate Dirac points can be splitinto a pair of Weyl points with opposite chiralities, and a Diracfermion splits into two Weyl fermions. Weyl fermions were originallyproposed in high energy physics, and their condensed matter physicscounterparts have been recently realized. Weyl semimetals exhibitintriguing properties, with open Fermi arcs connecting the Weyl pointsof opposite chiralities. Both Dirac and Weyl semimetals obey Lorentzinvariance and they exhibit anomalous negative magnetoresistance.

Recently, a new type of Weyl semimetal (type-II Dirac semimetals) havebeen predicted. In type-II Dirac semimetals, the Weyl points arise fromthe topologically protected touching points between electron and holepockets, and there are finite density of states at the Fermi level.Type-II Dirac semimetals have strongly tilted cone and thus violate theLorantzian invariance. However, so far, the spin-degenerate counterpartof type-II Dirac semimetals have not been realized.

What is needed, therefore, is a type-II Dirac semimetals and method formaking the same that overcomes the problems as discussed above.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with referenceto the following drawings. The components in the drawings are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the embodiments. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is a schematic section views of electron energy band of type-IDirac semimetal and type-II Dirac semimetal.

FIG. 2 is a flowchart of example I of a method for making a semimetalPtSe₂.

FIG. 3 is a schematic section view of example I of a device for making asemimetal PtSe₂.

FIG. 4 is a photo image of the semimetal PtSe₂ of example I.

FIG. 5 is a X-ray diffraction (XRD) result of the semimetal PtSe₂ ofexample I measured at room temperature.

FIG. 6 is a Raman spectrum result of the semimetal PtSe₂ of example Imeasured at room temperature.

FIG. 7 is a low energy electron diffraction (LEED) pattern of thesemimetal PtSe₂ of example I taken at beam energy of 70 eV.

FIG. 8 shows a measured in-plane two-dimensional Dirac cone of thesemimetal PtSe₂ of example I.

FIG. 9 shows a measured out-plane two-dimensional Dirac cone of thesemimetal PtSe₂ of example I.

FIG. 10 shows a calculated simulation result of two-dimensional Diraccone of the single crystal semimetal PtSe₂.

FIG. 11 shows a Brillouin zone of the semimetal PtSe₂ of example I.

FIG. 12 shows a measured three-dimensional Dirac cone of the semimetalPtSe₂ of example I.

FIG. 13 shows a calculated simulation result of three-dimensional Diraccone of the single crystal semimetal PtSe₂.

FIG. 14 is a flowchart of example II of a method for making a semimetalPtSe₂.

FIG. 15 is a schematic section view of example II of a device for makinga semimetal PtSe₂.

FIG. 16 is a photo image of the semimetal PtSe₂ of example II.

FIG. 17 is an X-ray diffraction (XRD) result of the semimetal PtSe₂ ofexample II measured at room temperature.

FIG. 18 is a Raman spectrum result of the semimetal PtSe₂ of example IImeasured at room temperature.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures, and components havenot been described in detail so as not to obscure the related relevantfeature being described. The drawings are not necessarily to scale, andthe proportions of certain parts may be exaggerated better illustratedetails and features. The description is not to be considered aslimiting the scope of the embodiments described herein.

The term “outside” refers to a region that is beyond the outermostconfines of a physical object. The term “inside” indicates that at leasta portion of a region is partially contained within a boundary formed bythe object. The term “substantially” is defined to essentiallyconforming to the particular dimension, shape or other word thatsubstantially modifies, such that the component need not be exact. Forexample, substantially cylindrical means that the object resembles acylinder, but can have one or more deviations from a true cylinder. Theterm “comprising” means “including, but not necessarily limited to”; itspecifically indicates open-ended inclusion or membership in aso-described combination, group, series and the like. It should be notedthat references to “an” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone.

References will now be made to the drawings to describe, in detail,various embodiments of the present type-II Dirac semimetals and methodfor making the same.

Example I

Referring to FIGS. 2-3, a self-flux method for making the semimetalPtSe₂ comprises following steps:

step (S10), placing pure Pt and pure Se in a reacting chamber 10 asreacting materials 13;

step (S11), evacuating the reacting chamber 10 to be vacuum less than 10Pa;

step (S12), heating the reacting chamber 10 to a first temperature of600 degrees Celsius to 800 degrees Celsius and keeping the firsttemperature for a period of about 24 hours to about 100 hours;

step (S13), cooling the reacting chamber 10 to a second temperature of400 degrees Celsius to 500 degrees Celsius and keeping the secondtemperature for a period of about 24 hours to about 100 hours at acooling rate from about 1 degrees Celsius per hour to about 10 degreesCelsius per hour to obtain a reaction product 15 comprising a crystalmaterial of PtSe₂; and

step (S14), separating the crystal material of PtSe₂ from the reactionproduct 15.

In step (S10), the reacting chamber 10 is a quartz tube having an openend and a sealed end opposite to the open end. The quartz tube is filledwith quartz slag 11 so that the quartz slag 11 form a support at thesealed end. The support has a thickness in a range of about 0.5centimeter to about 3 centimeters. In one embodiment, the thickness ofthe support is about 2 centimeters. The particle diameter of the quartzslag 11 is less than 1 millimeter. The inner diameter of the quartz tubeis about 8 millimeters, and the outer diameter of the quartz tube isabout 10 millimeters. The quartz tube is further filled with quartz wool12 so that the quartz wool 12 forms a filter on the quartz slag 11. Thefilter has a thickness in a range of about 0.5 centimeter to about 2centimeters. In one embodiment, the thickness of the filter is about 1centimeter. The diameter of the quartz wool 12 can be in a range ofabout 1 micrometer to about 10 micrometers. In one embodiment, thediameter of the quartz wool 12 is about 4 micrometers. The quartz slag11 and the quartz wool 12 separate the crystal material of PtSe₂ fromthe reaction product 15. The quartz slag 11 and the quartz wool 12 areoptional. If the quartz slag 11 and the quartz wool 12 are omitted, thereaction product 15 should be separated by special method, such as usinga metal filter or ceramic filter. The pure Pt and pure Se are filled inthe quartz tube after the quartz tube is filled with the quartz slag 11and the quartz wool 12. The molar ratio of Pt element and Se element isabout 2:80˜2:120. In one embodiment, the moral ration is Pt:Se=2:98. Thepure Pt and pure Se form the reacting materials 13. The purity of purePt is greater than 99.9%, and the purity of pure Se is greater than99.99%.

In step (S11), the quartz tube is evacuated by a mechanical pump andthen the open end of the quartz tube is sealed by fast heating the openend by a flame of natural gas and oxygen gas. In one embodiment, thepressure of the quartz tube can be less than 1 Pa. The natural gas canbe replaced by propane gas or hydrogen gas.

In step (S12), the quartz tube is reversed and vertically located sothat the reacting materials 13 is located at the bottom of the quartztube, and the quartz slag 11 and the quartz wool 12 are located at thetop of the quartz tube. The quartz tube is further accommodated in asteel sleeve 14. The fire-resistant cotton is filled between the quartztube and the steel sleeve 14 to fix and keep the temperature of thereaction product 15 in the quartz tube.

The steel sleeve 14, having the quartz tube therein, is placed in amuffle furnace. The quartz tube is heated by the muffle furnace to apoint where the inside thereof reaches 700 degrees Celsius and kept at48 hours at 700 degrees Celsius in the muffle furnace. During heating,the reacting materials 13 is kept at the bottom of the quartz tube andthe quartz slag 11 and the quartz wool 12 are kept at the top of thequartz tube. The quartz tube can also be heated by other heating devicerather than muffle furnace.

In step (S13), in one embodiment, the muffle furnace is cooled down to480 degrees Celsius at a cooling rate of 5 degrees Celsius per hour andkept at 48 hours at 480 degrees Celsius to obtain the reaction product15. The reaction product 15 includes the crystal material of PtSe₂ andthe excess reacting materials. The cooling rate can be in a range ofabout 1 degrees Celsius per hour to about 10 degrees Celsius per hour.

In step (S14), the steel sleeve 14, having the quartz tube therein, istaken out of the muffle furnace. Then the steel sleeve 14 is reversedand vertically located so that the quartz slag 11 and the quartz wool 12are located at the bottom of the quartz tube, and the reaction product15 is filed by the quartz wool 12. Thus, the excess reacting materialsare separated from the crystal material of PtSe₂.

Furthermore, the steel sleeve 14, having the quartz tube therein, can becentrifuged for a period in a range of about 1 minute to about 5 minutesat a speed in a range of about 2000 rpm/m to about 3000 rpm/m. In oneembodiment, the centrifuged period is about 2 minutes, and thecentrifuged speed is about 2500 rpm/m. The excessive reacting materialscan also be separated from the crystal material of PtSe₂ by othermethods after the reaction product 15 is taken out of the quartz tube.

The quartz tube is taken out of the steel sleeve 14 after naturalcooling. Then the crystal material of PtSe₂ is taken out of the quartztube, washed by chemical reagent to remove residual Se element, and thenrinsed by water to obtain pure crystal material of PtSe₂. The chemicalreagent can be hydrogen peroxide, dilute hydrochloric acid, sodiumhydroxide.

The pure crystal material of PtSe₂ of example I was tested. FIG. 4 is aphoto image of the semimetal PtSe₂ of example I. As shown in FIG. 4, thesemimetal PtSe₂ of example I is macroscopic visible and has a lengthabout 2 millimeters and a thickness about 10 micrometers to about 100micrometers. FIG. 5 is a XRD result of the semimetal PtSe₂ of example Imeasured at room temperature of about 15 degrees Celsius to about 25degrees Celsius. FIG. 6 is a Raman spectrum of the semimetal PtSe₂ ofexample I measured at room temperature. FIG. 7 is a LEED pattern of thesemimetal PtSe₂ of example I taken at beam energy of 70 eV. As shown inFIGS. 5 and 7, the semimetal PtSe₂ of example I confirm the high qualityof the single crystals. As shown in FIG. 7, the semimetal PtSe₂ ofexample I has a symmetrical structure. The Raman spectrum in FIG. 6shows Eg and A1g vibrational modes of the semimetal PtSe₂ of example Iat about 170 cm ⁻¹ and 210 cm ⁻¹ respectively, which are typical for 1Tstructure.

FIG. 8 shows a measured in-plane two-dimensional Dirac cone of thesemimetal PtSe₂ of example I measured at 22 eV. FIG. 9 shows a measuredout-plane two-dimensional Dirac cone of the semimetal PtSe₂ of example Imeasured at 22 eV. FIG. 10 shows a calculated simulation result oftwo-dimensional Dirac cone of the single crystal semimetal PtSe₂. FIG.11 shows a Brillouin zone of the semimetal PtSe₂ of example I. FIG. 12shows a measured three-dimensional Dirac cone of the semimetal PtSe₂ ofexample I. FIG. 13 shows a calculated simulation result ofthree-dimensional Dirac cone of the single crystal semimetal PtSe₂. Asshown in FIGS. 8-13, it is experimentally and theoretically confirmedthat the semimetal PtSe₂ of example I belong to Type-II Diracsemimetals.

The semimetal PtSe₂ of example I has physical properties such asnegative magnetoresistance, quantum spin Hall effect, and linear quantummagnetoresistance. As Type-II Dirac semimetals, the semimetal PtSe₂ ofexample I exhibits anomalous negative magnetoresistance.

Example II

Referring to FIGS. 14-15, a chemical vapor transport method for makingthe semimetal PtSe₂ comprises following steps:

step (S20), providing a PtSe₂ polycrystalline material;

step (S21), placing the PtSe₂ polycrystalline material in a reactingchamber 20 as reacting materials 23;

step (S22), placing chemical transport medium 26 in the reacting chamber20;

step (S23), evacuating the reacting chamber 20 to be vacuum less than 10Pa;

step (S24), placing the reacting chamber 20 at a temperature gradient,wherein the reacting chamber 20 has a first end 201 at a temperature ofabout 1200 degrees Celsius to about 1000 degrees Celsius and a secondend 202 opposite to the first end 201 and at a temperature of about 1000degrees Celsius to about 900 degrees Celsius; and

step (S25), keeping the reacting chamber 20 in the temperature gradientfor 10 days to 30 days to obtain the reaction product 25 at the secondend 202.

In FIG. 15, AB represents the element of PtSe₂, and L represents theelement of the chemical transport medium 26.

In step (S20), the PtSe₂ polycrystalline material can be provided by anymethod, In one embodiment, the PtSe₂ polycrystalline material is made byfollowing steps:

step (S201), placing pure Pt and pure Se in a quartz tube as reactingmaterials, wherein the molar ratio Pt:Se=1:2, the purity of pure Pt isgreater than 99.9%, and the purity of pure Se is greater than 99.9%;

step (S201), evacuating the quartz tube to be vacuum less than 10 Pa andthe quartz tube is sealed by fast heating;

step (S203), heating the quartz tube to a reacting temperature of 750degrees Celsius to 850 degrees Celsius and keeping the reactingtemperature for a period of about 50 hours to about 100 hours to obtainthe PtSe₂ polycrystalline material; and

step (S204), cooling the quartz tube to chamber temperature at a coolingrate in a range of about 10 degrees Celsius per hour to about 20 degreesCelsius per hour and taking the PtSe₂ polycrystalline material out ofthe quartz tube.

In step (S204), the PtSe₂ remains polycrystalline because the coolingrate is higher than 10 degrees Celsius per hour.

In step (S21), the reacting chamber 20 is a quartz tube having an openend and a sealed end opposite to the open end. The inner diameter of thequartz tube is about 8 millimeters, and the outer diameter of the quartztube is about 10 millimeters. The reacting materials 23 are located atthe sealed end of the quartz tube.

In step (S22), the chemical transport medium 26 can be located adjacentto the reacting materials 23. The chemical transport medium 26 can beSeBr₄, I₂, Br₂, Cl₂, SeCl₄. The concentration of the chemical transportmedium 26 can be in a range of about 5 mg/mL to about 20 mg/mL. In oneembodiment, the chemical transport medium 26 is SeBr₄ with aconcentration 10 mg/mL.

In step (S23), the quartz tube is evacuated and sealed by fast heatingas described above. The pressure of the quartz tube can be lower than 1Pa.

In step (S24), the quartz tube is horizontally located in the tubularfurnace 27. The reacting materials 23 are located at the first end 201of the quartz tube. The temperature of the first end 201 is higher thanthe temperature of the second end 202 so that the temperature gradientis formed between the first end 201 and the second end 202. In oneembodiment, the first end 201 of the quartz tube is heated by thetubular furnace 27 to a point where the inside thereof reaches 1050degrees Celsius, and the second end 202 of the quartz tube is heated bythe tubular furnace 27 to a point where the inside thereof reaches 970degrees Celsius.

In step (S25), the reaction product 25 can be obtained at the second end202 of the quartz tube after keeping the temperature gradient for 10days to 30 days. The reaction product 25 is taken out of the quartz tubeand washed using alcohol to remove the chemical transport medium toobtain pure crystal material of PtSe₂. In one embodiment, the reactingchamber 20 is kept in the temperature gradient for 20 days.

The pure crystal material of PtSe₂ of example II is tested. FIG. 16 is aphoto image of the semimetal PtSe₂ of example II. As shown in FIG. 16,the semimetal PtSe₂ of example II is macroscopic visible and has a sizeabout 2 millimeters. FIG. 17 is a XRD result of the semimetal PtSe₂ ofexample II measured at room temperature. FIG. 18 is a Raman spectrumresult of the semimetal PtSe₂ of example II measured at roomtemperature. As shown in FIG. 17, the semimetal PtSe₂ of example IIconfirm the high quality of the single crystals. The Raman spectrum inFIG. 18 shows Eg and A1g vibrational modes of the semimetal PtSe₂ ofexample I at about 170 cm⁻¹ and 210 cm⁻¹ respectively, which are typicalfor 1T structure. It is experimentally and theoretically confirmed thatthe semimetal PtSe₂ of example II belong to Type-II Dirac semimetals.

It is to be understood that the above-described embodiments are intendedto illustrate rather than limit the disclosure. Any elements describedin accordance with any embodiments is understood that they can be usedin addition or substituted in other embodiments. Embodiments can also beused together. Variations may be made to the embodiments withoutdeparting from the spirit of the disclosure. The above-describedembodiments illustrate the scope of the disclosure but do not restrictthe scope of the disclosure.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. It is also to be understood that the description and the claimsdrawn to a method may include some indication in reference to certainsteps. However, the indication used is only to be viewed foridentification purposes and not as a suggestion as to an order for thesteps.

What is claimed is:
 1. A method for making semimetal compound of Pt, themethod comprising: providing a quartz tube having an open end and asealed end opposite to the open end; filling quartz slag in the quartztube so that the quartz slag to form a support at the sealed end;filling quartz wool in the quartz tube so that the quartz wool to form afilter on the quartz slag; placing pure Pt and pure Se in the quartztube as reacting materials; evacuating the quartz tube to be vacuum witha pressure lower than 10 Pa; sealing the open end; verticallyaccommodating the quartz tube in a steel sleeve so that the reactingmaterials is located at a bottom of the quartz tube and the quartz slagand the quartz wool are located at a top of the quartz tube; heating thesteel sleeve to a first temperature of about 600 degrees Celsius toabout 800 degrees Celsius and keeping the first temperature for a firstperiod of about 24 hours to about 100 hours; cooling the steel sleeve toa second temperature of about 400 degrees Celsius to about 500 degreesCelsius and keeping the second temperature for a second period of about24 hours to about 100 hours at a cooling rate of about 1 degrees Celsiusper hour to about 10 degrees Celsius per hour to obtain a reactionproduct comprising a crystal material of PtSe₂; and separating thecrystal material of PtSe₂ from the reaction product by reversing thesteel sleeve.
 2. The method of claim 1, wherein a molar ratio of Ptelement and Se element is from 2:80 to 2:120.
 3. The method of claim 2,wherein the molar ratio of Pt element and Se element is 2:98.
 4. Themethod of claim 1, wherein a first purity of the pure Pt is greater than99.9%, and a second purity of the pure Se is greater than 99.99%.
 5. Themethod of claim 1, wherein the pressure is lower than 1 Pa.
 6. Themethod of claim 1, wherein the sealing the open end comprises fastheating the open end by a flame.
 7. The method of claim 1, wherein thevertically accommodating the quartz tube in the steel sleeve comprisesfilling fire-resistant cotton between the quartz tube and the steelsleeve.
 8. The method of claim 1, wherein the separating the crystalmaterial of PtSe₂ from the reaction product further comprisescentrifuging the reaction product.
 9. The method of claim 8, wherein aperiod of the centrifuging the reaction product is in a range from abouta minutes to about 5 minutes, and a speed of the centrifuging thereaction product is in a range of about 2000 rpm/m to about 3000 rpm/m.10. A method for making semimetal compound of Pt, the method comprising:placing pure Pt and pure Se in a reacting chamber as reacting materials;evacuating the reacting chamber to be vacuum with a pressure lower than10 Pa; heating the reacting chamber to a first temperature of about 600degrees Celsius to about 800 degrees Celsius and keeping the firsttemperature for a first period of about 24 hours to about 100 hours;cooling the reacting chamber to a second temperature of about 400degrees Celsius to about 500 degrees Celsius and keeping the secondtemperature for a second period of about 24 hours to about 100 hours ata cooling rate of about 1 degrees Celsius per hour to about 10 degreesCelsius per hour to obtain a reaction product comprising a crystalmaterial of PtSe₂; and separating the crystal material of PtSe₂ from thereaction product.